The present invention relates to a rotary compressor and, more particularly, to the control of the refrigerating capacity in air conditioner incorporating a rotary compressor.
Ordinary sliding vane type rotary compressors are finding spreading use in recent years as compressors for automobile air conditioners because of their small size and simple construction as compared with reciprocating type compressors having a large number of parts and complicated construction. In comparison with the reciprocating type compressors, however, the rotary compressors suffer the following disadvantages.
When the rotary compressor is used as a compressor for an automobile air conditioner, the power of the engine is transmitted to the pulley of a clutch for driving the compressor, through a belt running between the engine shaft and the pulley of the clutch. Therefore, when the sliding vane type compressor is used as a compressor for automobile air conditioners, its refrigerating capacity is increased substantially in proportion to the speed of revolution of the engine.
On the other hand, in the conventionally used reciprocating type compressors, the follow-up characteristics of the suction valve is deteriorate at the high speed of operation of the compressor, resulting in an insufficient sucking of the refrigerant gas into the cylinder, so that the refrigerating capacity is saturated when the speed of operation of the compressor is increased beyond a predetermined speed. Namely, in the reciprocating type compressors, there is a function of automatically suppressing the refrigeration capacity during high speed operation of the engine. In the rotary compressors, however, such a function cannot be performed so that the efficiency is lowered due to an increase of the compression work or the air is cooled excessively.
As a measure for overcoming the above-described shortcoming of the rotary compressor, it has been proposed to employ a solenoid-operated control valve in the passage leading to the suction port formed in a side plate of the compressor, the control valve being adapted to restrict the area of opening of the passage during high speed operation of the compressor to cause a suction loss and thereby to effect control of the refrigerating capacity. This arrangement, however, necessitates an additional provision of the control valve, resulting in a complicated construction and raised cost of production of the compressor. As another measure for eliminating the above-described shortcoming of the rotary compressors, it has been proposed also to employ a fluid clutch or a planetary gear system adapted to prevent the speed of revolution of the compressor from increasing beyond a predetermined level.
The arrangement using the fluid clutch, however, suffers a large energy loss due to generation of heat in the relative moving surfaces of the clutch, while in the arrangement making use of the planetary gear system, the size of the compressor is increased undesirably due to the incorporation of the planetary gear system, quite contrary to the current demand for simple and compact construction of the compressor in view of requirement for saving of energy. For these reasons, these countermeasures have not been put into practical use successfully.